Reviewed May 9, 2026
St. Augustine lawn care calendar
St. Augustinegrass needs careful timing because it is sensitive to stress, cold, disease pressure, and some herbicides.
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Spring: green-up, pre-emergent, and a careful first feeding
St. Augustine is the most herbicide-sensitive of the warm-season lawn grasses, so spring is as much about what you avoid as what you apply.
Pre-emergent (a product that stops weed seeds before they sprout, so it only works ahead of germination) goes down mid to late February for crabgrass and goosegrass. Refine the timing with your local soil temperature.
First nitrogen waits until May, or two weeks after green-up, whichever is later, at ½ pound of nitrogen per 1,000 square feet. Use a 3-1-2 or 4-1-2 N-P-K ratio if you do not have a soil test.
Mowing: keep it between 2½ and 4 inches. St. Augustine is mown high, not low: the height is what keeps it shading out weeds.
Herbicide warning: St. Augustine is sensitive to certain herbicides, 2,4-D in particular. Read the label and confirm St. Augustine is listed before anything goes in the sprayer. This is the single most common way people kill their own lawn.
Yellowing? If it is iron deficiency rather than a nitrogen shortage, NC State suggests ferrous sulfate at 2 ounces in 5 gallons of water per 1,000 square feet.
Large patch: spring fungicide is warranted starting when soil temperatures reach 55°F for four consecutive days.
Bare areas: replant in May with plugs on 12 to 24 inch centers, or sprigs at 1½ bushels per 1,000 square feet.
Summer: feeding, chinch bugs, and gray leaf spot
Feed on a light, steady schedule rather than in big doses: ½ pound of nitrogen per 1,000 square feet in June, 1 pound in July, and ½ pound in August.
Chinch bugs are the insect that does the most damage to St. Augustine. Check with the coffee can flotation test and treat if you find 20 or more chinch bugs per 1,000 square feet. Below that threshold, treating costs money without saving turf.
Gray leaf spot shows up in summer as small spots with gray centers ringed by a dark purple or brown border.
Thatch: if last summer's thatch was ¾ inch thick, mow down to 2½ inches and power rake with 3 inch blade spacing.
Post-emergent weed control only when the lawn is actively growing and not drought stressed, and still avoiding 2,4-D.
Fall and winter: stop early, then watch the soil temperature
St. Augustine is generally not fertilized after mid-September, and any September application should be ½ pound of nitrogen per 1,000 square feet or less.
Large patch prevention is the fall priority. Preventive fungicide starts when soil temperatures decline to 80°F and continues monthly until soil temperatures drop below 60°F. That is a soil temperature window, not a month, which is exactly why a printed calendar mistimes it.
Thatch check: measure in early September. If the layer is ¾ inch, plan to de-thatch next spring rather than now.
December through February: the lawn does not need mowing. Do not apply fertilizer or lime. Water occasionally so it does not dehydrate through a dry winter.
Annual ceiling: never more than 4 pounds of nitrogen per 1,000 square feet in a year.
St. Augustine fertilizer schedule at a glance
Rates are nitrogen per 1,000 square feet, from the NC State St. Augustinegrass maintenance calendar.
| When | What to apply | Rate |
|---|---|---|
| May, or 2 weeks after green-up (whichever is later) | Nitrogen (3-1-2 or 4-1-2) | ½ lb N |
| June | Nitrogen | ½ lb N |
| July | Nitrogen | 1 lb N |
| August | Nitrogen | ½ lb N |
| September (nothing after mid-month) | Nitrogen | ½ lb N or less |
| October to February | Nothing | — |
Annual ceiling: 4 pounds of nitrogen per 1,000 square feet.
Convert any of these into pounds of your actual bag with the fertilizer calculator.
St. Augustine watering schedule
Actively growing St. Augustine needs about 1 inch of water per week. On sandy soil, ½ inch every third day suits it better, because sand holds less.
In winter, water only occasionally, and only to stop the lawn dehydrating during a dry spell.
Work out how many minutes that is for your system with the irrigation runtime calculator.
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Common questions
- What is the St. Augustine fertilizer schedule?
- NC State Extension's calendar calls for a half pound of nitrogen per 1,000 square feet in May or two weeks after green-up (whichever is later), a half pound in June, 1 pound in July, and a half pound in August. September should be a half pound or less, and St. Augustine is generally not fertilized after mid-September. Never exceed 4 pounds of nitrogen per 1,000 square feet per year.
- How high should I mow St. Augustine grass?
- Maintain it between 2.5 and 4 inches. St. Augustine is a high-mown grass, and that height is part of how it shades out weeds.
- Which herbicides damage St. Augustine grass?
- St. Augustine is sensitive to certain herbicides, with 2,4-D specifically called out by NC State Extension. Always confirm St. Augustine is listed on the product label before spraying. This sensitivity is a common cause of self-inflicted lawn damage.
- How many chinch bugs before I need to treat?
- NC State's threshold is 20 or more chinch bugs per 1,000 square feet, checked with a coffee can flotation test. Below that, treatment is not warranted.
- When do I apply fungicide for large patch on St. Augustine?
- In spring, begin when soil temperatures reach 55°F for four consecutive days. In fall, preventive applications start when soil temperatures decline to 80°F and continue monthly until they drop below 60°F. Both are soil temperature triggers rather than calendar dates.
- How much water does St. Augustine need?
- About 1 inch per week while actively growing, or roughly a half inch every third day on sandy soils that hold less water.
UPDATED 2026-05-26